Discussion

Hurricane Arthur intensifies
Arthur continues to slowly intensify as it heads to the North Carolina coast having reached hurricane status in the overnight hours. The 11am readings on the storm are as follows: 90 mph max sustained winds, movement to the NNE at 10 mph, central pressure is now down to 28.97 inches. The category 1 hurricane could very well reach category 2 status before it reaches the Outer Banks of North Carolina later tonight as some additional strengthening is likely. Wind gusts of 100 mph are possible late tonight and early tomorrow on the Outer Banks as Arthur passes overhead. Arthur will begin to accelerate tonight as it turns to more of a northeasterly direction and its forward speed will continue to increase on Friday as it moves to higher latitudes. The simulated radar reflectivity for the next several hours (above) shows the heavier rain bands reaching the southern sections of the Outer Banks by early tonight (evacuations are underway). This simulated radar data is produced by an experimental high-resolution (3-km) computer forecast model at NOAA called the “High Resolution Rapid Refresh (HRRR)” [radar maps courtesy Weather Bell Analytics at weatherbell.com]. If Arthur makes landfall in the U.S. on Friday, it would be the first hurricane to do so on the Fourth of July, according to National Hurricane Center research that goes back to the 1850s.

Threat continues here for torrential downpours and severe thunderstorms
A very slow moving cold front will creep to the east coast by later today and this boundary zone will combine with an entrenched moisture-laden air mass, an upper-level short wave, and additional tropical moisture streaming northward from Arthur to produce off and on torrential downpours in the I-95 corridor from DC-to-Philly-to-NYC later today and tonight. In similar fashion to yesterday, showers and thunderstorms will begin to form during the mid-day hours over the higher terrain sections of central and western Pennsylvania, West Virginia, and western Virginia. Aided by lifting from an intensifying upper level jet streak, this initial area of showers and thunderstorms will then expand in coverage and intensity as the afternoon progresses resulting in widespread coverage by late in the day as the rainfall rolls to the east. Any storm that forms later today can reach severe levels with damaging wind gusts, hail and flash flooding due to an excessive amount of rainfall in a short period of time. The threat for torrential downpours in the I-95 corridor will continue through most of the night and then showers could linger into the morning hours on Friday as Arthur moves by well to the east of the Mid-Atlantic coastline. Drier air will push in later Friday as Arthur accelerates to the northeast to a position off of the New England coastline and then Saturday and Sunday will turn out to be great weather days throughout the Mid-Atlantic region. Rough surf and rip currents, however, could linger through the upcoming weekend in Mid-Atlantic coastal waters.